MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011
http://www.jpl.nasa.gov
IMAGE CAPTION P50084
September 15, 1998
Shapes of the Small Inner
Satellites of Jupiter
The upper series of images represents the best yet of the four small
inner satellites of Jupiter taken by the camera on NASA's Galileo
spacecraft. From left to right, in order of decreasing distance to
Jupiter, are Thebe, Amalthea (the largest moon), Adrastea (the
smallest), and Metis. The images represent the first time that the
shapes of Adrastea and Metis have been resolved by a spacecraft
camera.
The views are presented at a common scale but were taken at somewhat
different original resolutions, ranging from 5.4 kilometers (3.3
miles) per picture element for Amalthea, to 7.5 kilometers (4.6
miles) per picture element for Thebe and Metis. Individual craters,
35 to 90 kilometers (20 to 55 miles) across, are visible on Thebe
and Amalthea. While no craters are visible on Adrastea and Metis in
these images, the overall irregular shape of Metis indicates it has
suffered major collisions. Jupiter is to the right.
Viewing positions are slightly different from the views of the models
in the bottom row, which depict the shapes of the small satellites
viewed from the direction of satellite motion ("leading sides") and
presented at a common scale. These shape models have been calculated
from the outlines of the satellites and locations of shadows in
individual images, as well as from stereoscopic images taken by the
Galileo's camera during different orbits. The models emphasize the
highly irregular shapes caused by a history of impacts by fragments
of small asteroids and comets. Jupiter's strong gravitational pull
on these objects at relatively close distances accelerates the
objects to very high velocities, making such impacts very energetic.
JPL manages the Galileo mission for NASA's Office of Space Science,
Washington, DC. The images are posted on the Internet at
http://photojournal.jpl.nasa.gov/ and at
http://www.jpl.nasa.gov/galileo . Background information and
educational context for the images can be found at:
http://www.jpl.nasa.gov/galileo/sepo .
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9/9/98 JP